Add archify skill (v2.14), pi-mermaid ext (v0.3.0), project-diagramming-mermaid + project-diagramming-archify skills

- skills/archify: vendored tt-a1i/archify 2.14.0 (MIT), pure Node 18+, zero deps
- extensions/pi-mermaid: renders mermaid blocks as ASCII in TUI; deps beautiful-mermaid + mermaid
- skills/project-diagramming-*: orchestration skills, per-project docs/ convention

skills/archify/renderers/shared/layout-report.mjs

@@ -0,0 +1,40 @@
+/** Serialize computed layout for dry-run / inspect (#9). */
+
+export function componentBox(c) {
+  return {
+    id: c.id,
+    type: c.type,
+    label: c.label,
+    x: Math.round(c.x),
+    y: Math.round(c.y),
+    width: c.width,
+    height: c.height,
+    ...(Number.isInteger(c.row) ? { row: c.row } : {}),
+    ...(Number.isInteger(c.col) ? { col: c.col } : {}),
+    ...(Array.isArray(c.pos) ? { pos: c.pos.map(Math.round) } : {}),
+  };
+}
+
+export function boundaryBox(b) {
+  return {
+    kind: b.kind,
+    label: b.label,
+    x: Math.round(b.x),
+    y: Math.round(b.y),
+    width: Math.round(b.width),
+    height: Math.round(b.height),
+    wraps: b.wraps,
+  };
+}
+
+export function connectionPath(conn, routed, labelAt) {
+  return {
+    from: conn.from,
+    to: conn.to,
+    label: conn.label ?? null,
+    variant: conn.variant ?? 'default',
+    route: conn.route ?? 'auto',
+    points: routed.points.map(([x, y]) => [Math.round(x), Math.round(y)]),
+    ...(labelAt ? { labelAt: labelAt.map(Math.round) } : {}),
+  };
+}